A Novel Active Anode for Improved Photomultiplier Dynamic Range and Lifetime

Lead Research Organisation: University of Leicester
Department Name: Physics and Astronomy

Abstract

Despite advances in the performance of solid state photon counting devices, microchannel plate (MCP) photomultipliers remain the technology of choice for sub-200 picosecond event timing used in applications in particle and nuclear physics, and have application in other fields including life sciences, biological microscopy, for remote sensing and surveillance, materials analysis, fusion physics and space science instrumentation.

Current MCP photomultiplier designs have performance limitations which restrict their application. These are (i) limited maximum count rate, and (ii) limited detector lifetime.

We propose to add a gain stage behind the MCP stack by coating the anode with secondary electron emitting material, and collecting the charge on a mesh between the anode readout interface and MCP. An extra gain stage providing an amplification of ~10 would lower the gain required in the MCP stack by an order of magnitude, increasing both the local and global count rate limits imposed by the MCP and would further enhance the detector lifetime beyond that achieved by MCPs. The technique can be used with both conventional multi-anodes and the Image Charge technique can easily be adapted to provide gain by converting its resistive layer to a high emission dynode and inserting a transparent conductive mesh between MCP and dynode to act as an anode.

Suitable materials for a dynode material such as SiO2, Si3N4, Al2O3, MgO and BaO would be subject to charge-up. However ALD coating can overcome this problem by layering dopant materials to control the material resistivity.

A key issue in the proposed development is the deposition of thin film coatings with a tailored combination of electrical sheet resistance (100kohm per square - 100Mohm per square) and secondary electron emission. Candidate materials include alumina, magnesia and zinc oxide in their doped and pure compositions. ALD will be used in this project to prepare films on the MCP-dynode assemblies to be developed. ALD is a batch manufacturing process capable of highly conformal, pin-hole free and large area coatings. The technique has become a core manufacturing process for the deposition of 'high-k' dielectrics in current computer processor and memory devices where atomic control of thickness and uniformity is needed.

The Space Research Centre, University of Leicester, has long record of successful collaboration with Photek Ltd. focussed on development and commercialisation of novel concepts and techniques for photon counting, imaging detector systems. Photek have existing links with Professor Chalker at Liverpool and the proposed collaboration has already manufactured, characterised and tested a preliminary batch of ALD-coated samples which has provides promising technical justification for this proposal.

This collaboration has identified a novel technique of applying ALD coatings to enhance MCP photomultiplier dynamic range and lifetime which is patentable and highly complementary to existing devices. We have made preliminary measurements of candidate ALD coatings manufactured by Liverpool, demonstrated proof-of-concept of the image charge dynode/mesh anode gain technique in an MCP detector, and made a patent application to protect our IP.

We envisage that this technique, by providing significant detector dynamic range and lifetime benefits, will give Photek considerable advantage as detector providers for new projects at sLHC and FAIR. In addition the technique is applicable to many MCP-based photomultiplier designs for which there are significant markets in other areas including in fusion physics, remote sensing, life sciences, from biological R&D to clinical diagnostics, materials analysis and planetary science.

Publications

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Lapington J (2019) Modelling of picosecond timing signals from fast vacuum photodiodes in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Lapington J (2020) Investigating microchannel plate PMTs with TOFPET2 multichannel picosecond timing electronics in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

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Milnes J (2014) The TORCH PMT, a close packing, multi-anode, long life MCP-PMT for Cherenkov applications in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

 
Description Within this project we have developed a new technique to enhance the dynamic range and lifetime of microchannel plate (MCP) photomultipliers. These devices remain the technology of choice for sub-200 picosecond event timing used in applications in a variety of fields including particle and nuclear physics, the life sciences, biological microscopy, remote sensing and surveillance, materials analysis, fusion physics and space science instrumentation. Current MCP photomultiplier designs have performance limitations which restrict their application: (i) limited maximum count rate, and (ii) limited detector lifetime. 1. We have developed a technique which adds a gain stage behind the MCP stack by coating the anode with secondary electron emitting material, and collecting the charge on a mesh between the anode readout interface and MCP. 2. We have shown that this technique can achieve extra amplification allowing the MCP gain to be lowered, increasing both the local and global count rate limits imposed by the MCP. 3. We have demonstrated that atomic layer deposition (ALD) can be used in to manufacture emissive and resistive films on suitable substrates with high secondary electron emission (~6) and resistance suitable for imaging using the Image Charge technique. 4. We have also shown that the lowered MCP gain enhances the detector lifetime beyond that achieved by a conventional MCP stack. 5. We have shown that the technique can be used with both conventional multi-anode arrays and with the Image Charge technique, by adapting its resistive layer to a high emission dynode and inserting a transparent conductive mesh between MCP and dynode to act as an anode. 6. The Active Anode has recently been demonstrated with a state-of-the-art timing ASIC-based electronics system and achieved 100 picosecond single photon timing over a 256 pixel readout array.
Exploitation Route The "Active Anode" is a generic technology capable of extending both the dynamic range and the lifetime of MCP-based photomultipliers by an order of magnitude. These detectors are used in a wide range of academic research and commercial applications. We anticipate that this development will make a significant contribution in advancing academic research in fields where photon counting and imaging at high speed and high time resolution are crucial. These include: 1. Ring imaging Cherenkov detectors in particle physics 2. Ring imaging Cherenkov detectors in nuclear physics 3. Cherenkov detectors for inertial confinement fusion diagnostics 4. High content analysis - cell screening, flow cytometry, clinical diagnostics 5. Biological R&D - time correlated spectroscopy, time correlated single photon counting, fluorescence lifetime imaging, fluorescence correlation spectroscopy, confocal microscopy 6. Atmospheric chemistry and environmental monitoring -broad band cavity enhanced absorption spectroscopy for trace gas analysis 7. Remote sensing - LIDAR, 3D imaging, remote surveillance 8. Materials science - time of flight techniques including surface analysis techniques, molecular imaging, field ion microscopy (atom probe) 9. Space science - UV detectors for astronomy and planetary science - UV auroral imaging We also anticipate that this development will generate an enhanced market share in commercial applications of the above fields where photon counting imaging at high speed is required. We expect this development to lead to significant commercial return for Photek and UK industry using these detectors as system components. This project will also enhance the spin-out of STFC funded technology into other fields, enhancing cross-discipline collaborations between STFC and other sectors, and open pathways to further exploitation of STFC funded technologies.
Sectors Aerospace

Defence and Marine

Environment

Healthcare

Manufacturing

including Industrial Biotechology

Pharmaceuticals and Medical Biotechnology

Security and Diplomacy

Other

 
Description Microchannel plate based detectors are the major commercial technology available for photon imaging at time resolutions of 200 ps and below. The outcome of this project has been to significantly improve microchannel plate (MCP) detector dynamic range and lifetime by means of a novel technology, an "active anode" employing atomic layer deposition (ALD) to provide an additional gain stage after the MCP. The "Active Anode" is a generic technology capable of extending both the dynamic range and the lifetime of MCP-based photomultipliers by an order of magnitude. These detectors are used in a wide range of applications and given a successful outcome to this project we anticipate significant market share and commercial return for Photek as detector providers and UK industry using these detectors as system components. Though the project has officially completed we are continuing to work with our industrial collaborator (Photek) to develop the technique into a commercial product. The results of the project have been shared with the commercial partner and are being further investigated for potential commercial use in photomultiplier tubes. The technology has potential for economic and societal impacts in many areas of scientific research and commercial applications, including appication to ring imaging Cherenkov detectors for particle and nuclear physics, inertial confinement fusion diagnostics for fusion physics, remote sensing applications, applications in the life sciences, from biological R&D to clinical diagnostics, materials analysis and planetary science. Our commercial partner is exploring these opportunities. The project initiated further investigations into commercial applications of ALD processes in phootmultiplier tubes via a KTP project between the commercial partner and the University of Liverpool, co-applicants on this project, and experts in ALD techniques. The Active Anode technique is now being used (2019) with a timing ASIC, TOFPET2, for a picosecond timing high spatial resolution microchannel plate detector in collaboration with Photek Ltd. THe new detector concept, utilising a pixellated image readout with charge centroiding has applications in space science (UV astronomy, auroral imaging, space weather) and fast timing commercial opportunities. A poster was presented at the Vienna Conference on Instrumentation 2019 and a publication is in preparation.
First Year Of Impact 2014
Sector Aerospace, Defence and Marine,Electronics,Manufacturing, including Industrial Biotechology,Other
Impact Types Societal

Economic

 
Description A Novel Active Anode for Improved Photomultiplier Dynamic Range and Lifetime 
Organisation Photek Ltd.
Country United Kingdom 
Sector Private 
PI Contribution Detector development, material characterisation
Collaborator Contribution Materials deposition and characterisation Device design and manufacture
Impact This project is in early stages
Start Year 2013
 
Description A Novel Active Anode for Improved Photomultiplier Dynamic Range and Lifetime 
Organisation University of Liverpool
Country United Kingdom 
Sector Academic/University 
PI Contribution Detector development, material characterisation
Collaborator Contribution Materials deposition and characterisation Device design and manufacture
Impact This project is in early stages
Start Year 2013
 
Description TOFPET 
Organisation PETsys Electronics S.A.
Country Portugal 
Sector Private 
PI Contribution Evaluation of a multi-channel fast timing electronics system for applications requiring time resolved photon-counting spectroscopy.
Collaborator Contribution Collaboration in development of electronics and detectors for a photon-counting SPAD array for time resolved photon-counting spectroscopy.
Impact Development of a demonstrator system for prior to commercialisation. Report into performance of a multi-channel fast timing electronics system developed by Petsys electronics - medical pet detectors, s.a.
Start Year 2016
 
Description TOFPET 
Organisation Photek Ltd.
Country United Kingdom 
Sector Private 
PI Contribution Evaluation of a multi-channel fast timing electronics system for applications requiring time resolved photon-counting spectroscopy.
Collaborator Contribution Collaboration in development of electronics and detectors for a photon-counting SPAD array for time resolved photon-counting spectroscopy.
Impact Development of a demonstrator system for prior to commercialisation. Report into performance of a multi-channel fast timing electronics system developed by Petsys electronics - medical pet detectors, s.a.
Start Year 2016